Beam Dump Brennan GODDARD CERN ABBT The existing

Beam Dump Brennan GODDARD CERN AB/BT The existing LHC beam dump is described, together with the relevant design aspects, technological and operational limitations. The issues and challenges presented by the various LHC luminosity upgrade options are detailed, together with some possible upgrade paths. Thanks to V. Mertens, E. Vossenberg. B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Outline of talk • Existing LHC beam dumping system – overview, parameters, design aspects and limitations; • Issues and challenges of LHC luminosity upgrades – Extraction, dilution, absoption, protection; • Possible beam dump upgrade paths • Conclusion B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Present system - concept extract dilute dump • Loss-free fast extraction system – Laminated steel kickers; DC Lambertson septum; • Dilution system – Laminated steel kickers; passive ~650 m drift length. • Beam dump (absorber) block – Graphite cylinder, steel and concrete shielding • Protection devices – Graphite protection (dilution) for septum and LHC machine B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Present design - schematic layout TDE dump block 10 x MKB kickers 15 x MSD septa TCDS protection TCDQ protection Total ‘beamline’ length : 975 m from kicker MKD to dump TDE B. Goddard 08/11/04 HHH 2004 Workshop, CERN 15 x MKD kickers

Present design - tunnel layout Dump cavern 40 m Total ‘beamline’ length : 975 m from kicker MKD to dump block TDE B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Present design – main parameters System Installed length [m] Field [T] System kick [mrad] MKD extraction kickers 27 0. 3 0. 28 MSD extraction septa 73 0. 8 - 1. 2 2. 40 MKBH dilution kicker 11 0. 85 ± 0. 14 MKBV dilution kicker 11 0. 85 ± 0. 14 Septum protection 7 - - Q 4 / LHC protection 12 - - Parameter Unit Value Total beamline length (start MKD – end TDE) m 975 Particle-free abort gap ms 3. 0 Beta function at beam dump block TDE (H / V) m 5000 Beam size at TDE - 1 s (H / V) mm 1. 5 Sweep length on TDE face cm 109 Maximum temperature in TDE graphite ˚C 1250 B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Present system – TDE absorber 0. 7 m 7. 7 m C cylinder B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Present system – TDE absorber – Density is graded to minimise DT: graphite with r = 1. 8 - 1. 1 - 1. 8 g/cc – Full sweep DT = 1250 OC in the dump block (LHC ultimate 0. 86 A, 7 Te. V) B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Present system - protection – Unsynchronised dump would destroy septum and downstream elements – 2 long (6 m), low density (carbon) absorbers to intercept undiluted bunches B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Present system - limitations • Extraction system – Intensity : not limited – Energy : 7. 5 Te. V by kicker and septum strength – Filling scheme : not limited (need 3 ms abort gap) • Dilution system – Intensity : not limited; – Energy : limited to 7. 5 Te. V by kicker strength – Filling scheme : fails for superbunch (sweep length) B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Present system - limitations • Beam dump absorber block – Intensity : 1 A (at 7 Te. V) with DT max of ~1500 OC – Energy : 7. 5 Te. V (at 0. 7 A) with DT max of ~1500 OC – Filling scheme : not limited (if adequate dilution). • Protection devices – Intensity : 1 A at 7 Te. V by DT in septum and Q 4 – Energy : 7. 5 Te. V (at 0. 7 A) by DT in septum and Q 4 – Filling scheme : protection fails for superbunch. B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Increasing Intensity to 1. 7 A - issues • Extraction system – Kicker - no problems (unless RF heating? ? ). Feasible – Septum – no problems. Feasible • Dilution system – x 2 sweep length. Feasible • Beam dump Absorber block – Reduce DT max by reduced C density. Feasible • Protection devices – Reduce DT max by reduced C density. B. Goddard 08/11/04 HHH 2004 Workshop, CERN Feasible

Increasing Energy to 14 Te. V - issues • Extraction system – Kicker x 2 B. dl – x 2 length or x 2 rise-time (6 ms). Feasible – Septum x 2 B. dl – x 2 length. Feasible • Dilution system – x 4 sweep x 4 kicker f 0; plus x 2 B. dl x 8 length. Difficult – Increase dump tunnel length Difficult • Beam dump Absorber block – Reduce DT max by reduced C density – x 4 length. Difficult • Protection devices – Reduce DT max by reduced C density – x 4 length. Difficult B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Superbunch with 0. 86 A - issues • Extraction system – Kicker - no problems. Feasible – Septum – no problems. Feasible • Dilution system – x 100 sweep length. Impossible • Beam dump Absorber block – Reduce DT max with C density – increase length. Feasible • Protection devices – Dilute full beam current without damage. B. Goddard 08/11/04 HHH 2004 Workshop, CERN Impossible

Upgrades – Higher I at 7 Te. V • Total intensity in distributed bunches • Upgrades required for dump system – Increase sweep length (higher f 0 more dilution kickers) – Upgrade dump block (longer, lower density C); – Upgrade protection devices (longer, lower density C, more lr). • Feasible for 1. 7 A with ‘modest’ upgrades (e. g. avoiding civil engineering) B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Upgrades – 14 Te. V • Intensity in distributed bunches • Considerable upgrades required for dump system – Increase kicker and septum strength (6 ms kicker rise time OR x 2 kickers; x 2 septa) – Increase dilution sweep length higher f 0, more kickers OR SC dilution quadrupole OR longer beam dump tunnel – Upgrade dump block (longer, lower density) – Upgrade protection devices (longer, sacrificial elements) • Main Challenges – Beam dilution and energy deposition in dump block (small spot) – Machine protection for failure cases (slower rise time bad) B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Upgrades – superbunch • All intensity in 1 ms superbunch at 7 Te. V • Major dump system upgrades required – Dilution with SC quadrupole – Upgrade dump block (longer, lower density C, larger diameter) – Lengthen (+500 m) and possibly widen dump tunnel; new cavern – Sacrificial protection devices OR 100% reliable ‘active’ machine protection… • Main challenges – Achieving sufficient dilution (sweeping beam impossible) – Machine protection against synchronisation error B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Dilution with spiral sweep • Increase dilution kicker frequency and sweep length – 14 to 56 k. Hz… would require ~4 times more kicker length 108 cm sweep length 400 cm sweep length – At 7 Te. V would allow currents of ~3 A in distributed bunches – At 14 Te. V would allow ~0. 8 A in distributed bunches B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Dilution with SC quadrupole 20 m quad @ 200 T/m Present optics b max ~5 km, s ~1. 5 mm Dilution quad b max ~1000 km, s ~20 mm – Works for any filling pattern : s constant at ≈ 20 mm (need ‘squeeze’) – Need extra 500 m beam dump tunnel…. – Quad design ~OK : L 20 m @ 200 T/m, ~70 mm aperture – Very orbit sensitive : 2 mm 0. 35 mrad ~0. 4 m at dump (1150 m drift). • Absorber block size : ≈ 1. 5 m (± 0. 5 m orbit, ± 0. 25 m for 8 s beam) B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Protection – difficult with increasing E – Low material density essential to avoid material damage – More total material required to dilute energy density – Very long objects as a result… Peak Ge. V/cc in Cu vs beam size at 450 Ge. V and 7 Te. V – 107 dilution factor, need ~16 lr of C 1. 8 g/cc, or ~6 m at 7 Te. V. 3. 31 4. 5 – For 107 at 14 Te. V, ~0. 8 g/cc to avoid damage 14 m. – Some optimisation with graded density to get more lr 1. 77 1. 4 1. 77 DT and density in LHC diluter for 7 Te. V sweep (47 bunches) B. Goddard 08/11/04 HHH 2004 Workshop, CERN

Conclusion • Dump upgrade for ~1. 7 A at 7 Te. V looks feasible – Some changes to dilution, absorption and protection • Upgrading for 0. 8 A superbunch is more difficult: – Achieving sufficient dilution to allow safe absorption (SC quadrupole dilution, absorber, tunnel, cavern, orbit…) – Machine protection (use sacrificial elements? depends on reliability…) B. Goddard 08/11/04 HHH 2004 Workshop, CERN